Option 1. Use GF mergetags inside normal page or post content.
Since v1.1 it is possible to configure redirect pages. These are pages the user will be redirected to after completing or cancelling the payment.
You can use any page and display entry data by using the normal gravity forms merge tags.
See below example where I used blocks to create a simple page. Here I am showing the First name from the entry and also all the fields that were submitted in the form.
Note: This method may not work with visual page builders. If that is the case then please refer to option 2 below.
Option 2. Use the gfcc_mergetags shortcode
The mergetags method described in option 1 may not always work with all visual page builders. To solve this, I have created the new shortcode. Its an enclosing shortcode as you can see and inside the shortcode you can use the normal mergetags of gravity forms again.
See below example of how you can use this shortcode with merge tags. The output on the frontend will be the same as in the first method described.